ESR1 and neoplasm: Through the RAS–RAF–MEK–ERK signaling pathway, the MYC/c-MYC protein is involved in cell proliferation and angiogenesis; through the WNT, ESR/JUP–FOS/JUN/SP1/NCOA/ESR, and MYC/c-MYC–CCND–RB1–E2F signaling pathways, it is involved in cell proliferation; and through MYC/c-MYC–E2F signaling pathway, it plays a role in blocking cell differentiation [14,61], which are very important in the progression of tumor processes.